Development device, charging method used in the development device and image forming device having the development device

Abstract

An image forming device includes a development section which has a blade for applying electrons generated in its photoelectric surface due to a photoelectric effect to a toner so as to charge the toner; an ultraviolet irradiator for irradiating the photoelectric surface with light; a development roller for holding the toner thus charged, and performing carriage of the toner to a photoconductive drum having an electrostatic latent image on a surface; wherein the electrostatic latent image on the photoconductive drum is developed by the charged toner. The development section further includes a control section for performing control of application of a voltage to the ultraviolet irradiator, application of a voltage to the photoelectric surface, application of a voltage to the development roller, and beginning of the carriage of the toner by the development roller, at predetermined timings, respectively.

What is claimed is:  
     
       1. A development device, comprising: 
       a charging section having an electron emission section and applying electrons generated in the electron emission section due to a photoelectric effect to a developer so as to charge the developer;  
       an irradiation section for irradiating the electron emission section with light so as to cause the electron emission section to generate the electrons;  
       a developer carriage section for holding the developer thus charged, and performing carriage of the developer to a latent image holding body having an electrostatic latent image on a surface; and  
       a control section for performing control of (a) application of a voltage to the irradiation section, (b) application of a voltage to the electron emission section, (c) application of a voltage to the developer carriage section, and (d) beginning of the carriage of the developer by the developer carriage section, at predetermined timings, respectively,  
       the electrostatic latent image on the latent image holding body being developed by the developer which has been charged.  
     
     
       2. The development device as set forth in  claim 1 , wherein: 
       the control section performs the control so that the (b) application of a voltage to the electron emission section is carried out when irradiation quantity from the irradiation section becomes substantially constant after the (a) application of a voltage to the irradiation section.  
     
     
       3. The development device as set forth in  claim 1 , wherein: 
       the control section performs the control so that the (c) application of a voltage to the developer carriage section is carried out when a predetermined time period is elapsed after the (b) application of a voltage to the electron emission section.  
     
     
       4. The development device as set forth in  claim 3 , wherein: 
       the predetermined time period is a time period until electron emission from the electron emission section becomes stabilized after the (b) application of a voltage to the electron emission section.  
     
     
       5. The development device as set forth in  claim 1 , wherein: 
       the control section performs the control so that the (d) beginning of the carriage of the developer by the developer carriage section is carried out after the (c) application of a voltage to the developer carriage section.  
     
     
       6. The development device as set forth in  claim 1 , wherein: 
       the electron emission section is made of a semiconductor or a metal.  
     
     
       7. The development device as set forth in  claim 6 , wherein: 
       the electron emission section is provided by forming the semiconductor or the metal on a base material of the charging section.  
     
     
       8. The development device as set forth in  claim 7 , wherein: 
       the base material of the charging section is made of a base which has ultraviolet permeability and coated with a material having ultraviolet permeability and conductivity.  
     
     
       9. The development device as set forth in  claim 1 , wherein: 
       the electron emission section has a plate-shaped surface, which is provided to be opposite to the developer carriage section.  
     
     
       10. The development device as set forth in  claim 1 , wherein: 
       a bias voltage is applied between the electron emission section and the developer carriage section.  
     
     
       11. The development device as set forth in  claim 1 , wherein: 
       the charging section includes a thickness control section for controlling a thickness of the developer on the developer carriage section to be a constant thickness.  
     
     
       12. The development device as set forth in  claim 11 , wherein: 
       the thickness control section is provided on an upstream portion of the electron emission section in a developer carriage direction of the developer carriage section.  
     
     
       13. The development device as set forth in  claim 11 , wherein: 
       the developer carriage section opposite to the thickness control section has a greater surface roughness than that of the thickness control section opposite to the developer carriage section.  
     
     
       14. The development device as set forth in  claim 1 , wherein: 
       voltage difference Va (V) between the electron emission section and the developer carriage section satisfies Va<312+6.2×1 where a distance between the electron emission section and the developer carriage section is 1 (μm).  
     
     
       15. A charging method for charging a developer so as to develop an electrostatic latent image into a developer image, comprising the step of: 
       carrying out image forming by supplying the developer, which has been charged, to a latent image holding body having the electrostatic latent image on a surface, and transferring the developer image from the latent image holding body to a recording medium,  
       wherein:  
       (a) application of a voltage to an irradiation section which performs light irradiation, (b) application of a voltage to an electron emission section which induces electrons thereof by a photoelectric effect with the light irradiation, so as to discharge the electrons, (c) application of a voltage to a developer carriage section which performs carriage of the developer to the latent image holding body having the electrostatic latent image on the surface, and (d) beginning of the carriage of the developer by the developer carriage section, are carried out at predetermined timings, respectively.  
     
     
       16. The charging method as set forth in  claim 15 , wherein: 
       the (a) application of a voltage to the irradiation section, the (b) application of a voltage to the electron emission section, the (c) application of a voltage to the developer carriage section, and the (d) beginning of the carriage of the developer by the developer carriage section, are carried out in this order.  
     
     
       17. The charging method as set forth in  claim 16 , wherein: 
       the (b) application of a voltage to the electron emission section is carried out when irradiation quantity from the irradiation section becomes substantially constant after the (a) application of a voltage to the irradiation section.  
     
     
       18. The charging method as set forth in  claim 16 , wherein: 
       the (c) application of a voltage to the developer carriage section is carried out when a predetermined time period is elapsed after the (b) application of a voltage to the electron emission section.  
     
     
       19. The charging method as set forth in  claim 18 , wherein: 
       the predetermined time period is a time period until electron emission from the electron emission section becomes stabilized after the (b) application of a voltage to the electron emission section.  
     
     
       20. The charging method as set forth in  claim 16 , wherein: 
       the (d) beginning of the carriage of the developer by the developer carriage section is carried out after the (c) application of a voltage to the developer carriage section.  
     
     
       21. The charging method as set forth in  claim 15 , wherein: 
       a bias voltage is applied between the electron emission section and the developer carriage section.  
     
     
       22. The charging method as set forth in  claim 15 , wherein: 
       a thickness of the developer on the developer carriage section is controlled to be a constant thickness.  
     
     
       23. The charging method as set forth in  claim 15 , wherein: 
       the (a) application of a voltage to the irradiation section, the (b) application of a voltage to the electron emission section, the (c) application of a voltage to the developer carriage section, and the (d) beginning of the carriage of the developer by the developer carriage section, are carried out before the image forming.  
     
     
       24. An image forming device, comprising: 
       a latent image holding body for holding a electrostatic latent image which is formed based on an image signal; and  
       a development device including (i) a charging section for applying electrons generated in an electron emission section due to a photoelectric effect to a developer, so as to charge the developer, (ii) an irradiation section for irradiating the electron emission section with light, (iii) a developer carriage section for holding the developer which has been charged, and performing carriage of the developer to the latent image holding body, and (iv) a control section for performing control of (a) application of a voltage to the irradiation section, (b) application of a voltage to the electron emission section, (c) application of a voltage to the developer carriage section, and (d) beginning of the carriage of the developer by the developer carriage section, at predetermined timings, respectively,  
       the development device developing the electrostatic latent image on the latent image holding body to a developer image with the developer which has been charged.  
     
     
       25. The image forming device as set forth in  claim 24 , wherein: 
       the control section carries out the (a) application of a voltage to the irradiation section, the (b) application of a voltage to the electron emission section, the (c) application of a voltage to the developer carriage section, and the (d) beginning of the carriage of the developer by the developer carriage section, in this order.  
     
     
       26. The image forming device as set forth in  claim 25 , wherein: 
       the control section carries out the (b) application of a voltage to the electron emission section when irradiation quantity from the irradiation section becomes substantially constant after the (a) application of a voltage to the irradiation section.  
     
     
       27. The image forming device as set forth in  claim 25 , wherein: 
       the control section carries out the (c) application of a voltage to the developer carriage section when a predetermined time period is elapsed after the (b) application of a voltage to the electron emission section.  
     
     
       28. The image forming device as set forth in  claim 25 , wherein: 
       the predetermined time period is a time period until electron emission from the electron emission section becomes stabilized after the (b) application of a voltage to the electron emission section.  
     
     
       29. The development device as set forth in  claim 25 , wherein: 
       the control section carries out the (d) beginning of the carriage of the developer by the developer carriage section after the (c) application of a voltage to the developer carriage section.  
     
     
       30. The image forming device as set forth in  claim 25 , wherein: 
       the control section starts the application of a voltage to the irradiation section immediately after an image forming request is made by a user.  
     
     
       31. The image forming device as set forth in  claim 24 , wherein: 
       after an image forming request is made by a user, the control section carries out initialization operation of the image forming device together with the control, before starting image forming by forming the electrostatic latent image on the latent image holding body.  
     
     
       32. The image forming device as set forth in  claim 31 , further comprising: 
       a transfer section electrically connected to a surface of the latent image holding body via a recording medium by being in contact with the recording medium, and transfers the developer image to the recording medium;  
       a fixing device for fixing the developer to the recording medium through thermal fixing; and  
       a carriage section for carrying the recording medium,  
       the initialization operation including warm-up of the fixing device, adjustment of a residual voltage of the latent image holding body, and detection of presence or absence of the recording medium on the carriage section.  
     
     
       33. The image forming device as set forth in  claim 24 , wherein: 
       the control section applies a voltage to the irradiation section, and after a predetermined time is elapsed, applies a voltage to the electron emission section, the predetermined time being previously decided according to a cumulative number of image forming on the recording medium in the image forming device.  
     
     
       34. The image forming device as set forth in  claim 24 , further comprising: 
       a transfer section electrically connected to a surface of the latent image holding body via a recording medium by being in contact with the recording medium, and transfers the developer image to the recording medium;  
       a fixing device for fixing the developer to the recording medium through thermal fixing; and  
       a carriage section for carrying the recording medium,  
       after image forming of the recording medium is finished by transferring the recording medium to the fixing device, the control section stopping the (a) application of a voltage to the irradiation section, the (b) application of a voltage to the electron emission section, the (c) application of a voltage to the developer carriage section, and the (d) beginning of the carriage of the developer by the developer carriage section, at predetermined timings, respectively, so as to carry out stopping operation of the development device, the stopping operation being carried out together with final operation in the image forming device, which is required to be carried out before setting the image forming device to be back in a standby state.  
     
     
       35. The image forming device as set forth in  claim 34 , wherein: 
       the control section stops the (d) beginning of the carriage of the developer by the developer carriage section, the (c) application of a voltage to the developer carriage section, the (b) application of a voltage to the electron emission section, and the (a) application of a voltage to the irradiation section, in this order so as to carry out the stopping operation.  
     
     
       36. The image forming device as set forth in  claim 34 , wherein: 
       the final operation includes removal of a residual voltage of the latent image holding body, detection of presence or absence of the recording medium on the carriage section, and removal of the developer remaining on the latent image holding body.